Type a pattern, paste some text, see matches highlight in real time. Rambler reads your regex aloud — "match one or more digits, then a dash, then…" — so you know exactly what it does before you commit it to production.
It walks through your regex token by token and describes each piece in plain English. Not a replacement for learning regex, but it's much faster than mentally simulating \b[A-Z][a-z]*\b every time.
g for finding all matches (default). i for case-insensitive. m so that ^ and $ match per line. s to let . match newlines. u for unicode-aware matching.
Three common reasons. One: you forgot the g flag and are only seeing the first match. Two: you're using . but your text has newlines (add s). Three: you need \s for spaces, not literal spaces in character classes.
(abc) is a capturing group — you can reference it later via $1, \1, etc. (?:abc) is non-capturing — it groups for operators like + or | but doesn't store the match. Use non-capturing when you don't need the value back.
JavaScript's RegExp. Very close to PCRE but with some differences — no lookbehind in older browsers, no possessive quantifiers, different named group syntax. If you paste a PHP or Python pattern, some things may not work. Ask in the URL bar.
Yes — nested quantifiers like (a+)+ can hang the engine. Rambler runs every pattern with a 100ms timeout guard. If your regex is too slow, you'll get an error instead of a frozen tab.